problem with VSS checkin

[bnl]

I'm trying to create a step to checkin any files that have been checked out from sourcesafe.

The step runs through all of the projects in the tree and checks in any files that are checked out.

Then at the very end it prints this:

Project $5.21 has been destroyed, and cannot be rebuilt.
Continue anyway?(Y/N)N

Process completed with exit code 100
12/30/2003 3:01:06 PM: Step 'Checkin Files' failed
12/30/2003 3:01:06 PM: Build ended.

When I run the SSHELPER.exe directly it does the same thing.
sshelper.exe y:\path Checkin "$/Main" -GL"C:\Development\Main" -GWS -GTM -GCK -R -NL -I-N -Yaaa, -W- -C-


When I run the source safe command from a dos prompt it works fine.
"C:\Program Files\Microsoft Visual Studio\Common\VSS\win32\ss.exe" Checkin "$/Main" -GL"C:\Development\Main" -GWS -GTM -GCK -R -NL -I-N -Yaaa, -W- -C-

What is going on here? What extra is sshelper doing that ss.exe isn't? Is there any way to make this task pass without forcing answering yes to the prompt?